Funds are requested for the purchase of a single crystal X-ray diffractometer with a high power rotating anode generator and a low temperature accessory. The present facility is an old diffractometer with a weak conventional X-ray source. It is controlled by a twenty-year old, obsolete computer, which fails increasingly often and is difficult to repair for lack of spare parts. This requested instrumentation will enable for the first time 8 investigators at Emory University associated with 13 NIH supported research programs to garner detailed structural information at an atomic level for a myriad of crystalline samples which are (i) too small (< 0.1 mm average side) (ii) too weakly diffracting, or (iii) too unstable with respect to desolvation or thermal decomposition to be examined by the existing X-ray crystallographic capabilities at Emory. The acquisition of detailed X-ray crystallographic structural information is now a success limiting factor in a number of programs and the requested instrumentation will have immediate as well as lasting impact on the efficacy of considerable funded research. Affected NIH programs include (i) the development of anti-AIDS agents and diagnostic agents for renal imaging, (ii) the synthesis of anticancer drugs, molecular probes of DNA structure, and model compounds of iron centers in metalloproteins, and (iii) the investigation of molecular aggregates related to lipids. The X-ray facility will be housed in the Chemistry Department, and carefully run and maintained by in-house staff who will be trained for this purpose. The facility will be made available to a number of other biomedical investigators at Emory University's sister institutions (Emory Medical School, the Centers for Disease Control, the American Cancer Society, the Emory Yerkes Primate Center, and the Veteran's Administration Medical Center) and to other NIH-funded investigators in the Atlanta area.